ARLINGTON, Virginia — Former House speaker Newt Gingrich on Wednesday dropped his erratic campaign for the 2012 Republican presidential nomination, but pledged to remain in the public eye as an "active citizen."

"Today I am suspending the campaign. Suspending the campaign does not mean suspending citizenship," Gingrich said in a speech in the Washington suburb of Arlington, Virginia.

His exit leaves only Ron Paul, a Texas congressman who represents the libertarian wing of the party, in the race against the almost certain nominee Mitt Romney.

Gingrich, best known for his polarizing term as leader of the House of Representatives in the 1990s, enjoyed brief spurts of success after a chaotic start to his presidential campaign.

But ultimately he won just two nominating contests since the start of the state-by-state race in January -- in his home state Georgia and in South Carolina -- and was a distant third in the fight to take on US President Barack Obama in November.

Former US senator Rick Santorum, who overtook Gingrich as the Republicans' favorite alternative to Romney, quit the race last month.

Paul remains a fringe candidate, consistently placing fourth in the primary season and with no chance of catching Romney, who has effectively embarked on a general election campaign against the Democratic incumbent.

Gingrich, deeply critical of Romney during the nomination race, buried the hatchet in his resignation, saying his old rival was better than Obama, who is seeking a second term.

"As to the presidency, I am asked sometimes -- is Mitt Romney conservative enough? My answer is simple -- compared to Barack Obama?" Gingrich said.

"This is not a choice between Mitt Romney and Ronald Reagan. This is a choice between Mitt Romney and the most radical, leftist president in American history."

Gingrich touted himself as an intellectual with conservative roots going back to the Reagan years and a debater able to make mincemeat of Obama.

However, his multiple marriages and erratic record on policy positions made the Republican right mistrust him, while his love of public speaking tended to translate into lecturing, rather than inspiring speeches.

Romney was generous in his latest victory, declaring that the departed Gingrich "demonstrated both eloquence and fearlessness in advancing conservative ideas."

Gingrich "long ago created an enduring place for himself in American history," Romney stated.

Gingrich said he would work to advance Romney's battle against Obama and his party's bid to defeat Democrats in Congress.

"A Republican sweep this fall would revitalize America just as the Reagan sweep of 1980 revitalized America. We have done it before. We can do it again," Gingrich said.

"I always tell people that economic recovery will begin late on election night when people realize that Obama is gone. By the next morning, people will make new decisions about investing, hiring."